1. heap-inl.h has a function Heap::_inline_get_heap_ that calls
Isolate::Current() defined in isolate.h, so heap-inl.h requires
isolate.h.

2. Isolate has an embedded Heap member, so isolate.h requires heap.h.

3. heap.h has inline functions functions defined that call
Heap::_inline_get_heap_, so heap.h requires heap-inl.h (!).

The upshot is that all three need to be included wherever one is.  A
simpler way is to break the cycle by moving the inlined functions in
heap.h to heap-inl.h.

R=vegorov@chromium.org
BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/9121033

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@10539 ce2b1a6d-e550-0410-aec6-3dcde31c8c00